Are We Headed Towards Another Deep Solar Minimum?
Have you been keeping an eye on Sol lately? One of the top astronomy stories for 2018 may be what’s not happening, and how inactive our host star has become. The strange tale of Solar Cycle #24 is ending with an expected whimper: as of May 8th, the Earthward face of the Sun had been spotless for 73 out of 128 days thus far for 2018, or more than 57% of the time. This wasn’t entirely unexpected, as the solar minimum between solar cycle #23 and #24 saw 260 spotless days in 2009 – the most recorded in a single year since 1913. Cycle #24 got off to a late and sputtering start, and though it produced some whopper sunspots reminiscent of the Sol we knew and loved on 20th century cycles past, it was a chronic under-performer overall. Mid-2018 may see the end of cycle #24 and the start of Cycle #25… or will it? The story thus far… and the curious drama that is solar cycle #24. Credit: David Hathaway/NASA Marshall Spaceflight Center. One nice surprise during Cycle #24 was the appearance of massive sunspot AR 2192, which popped up just in time for the partial solar eclipse of October 23rd, 2014. Several times the size of the Earth, the spot complex was actually the largest seen in a quarter century. But just as “one swallow does not a Summer make,” one large sunspot group couldn’t save Solar Cycle #24. The partial eclipse of the Sun, October 23, 2014, as seen from Jasper, Alberta, shot under clear skies through a mylar filter, on the front of a 66mm f/6 apo refractor using the Canon 60Da for 1/8000 (!) sec exposure at ISO 100. The colors are natural, with the mylar filter providing a neutral “white light” image. The big sunspot on the Sun that day is just beginning to disappear behind the Moon’s limb. The mylar filter gave a white Sun, its natural colour, but I have tinted the Sun’s disk yellow for a more pleasing view that is not just white Sun/black sky. Image credit and copyright: Alan Dyer/Amazing Sky.net The Sun goes through an 11-year sunspot cycle, marked by the appearance of new spots at mid- solar latitudes, which then slowly progress to make subsequent appearances closer towards the solar equator, in a pattern governed by what’s known as Spörer’s Law. The hallmark of a new solar cycle is the appearance of those high latitude spots. The Sun actually flips overall polarity every cycle, so a proper Hale Cycle for the Sun is actually 11 x 2 = 22 years long. A big gaseous fusion bomb, the Sun actually rotates once every 25 days near its equator, and 34 days at the poles. The Sun’s rotational axis is also tipped 7.25 degrees relative to the ecliptic, with the northern rotational pole tipped towards us in early September, while the southern pole nods towards us in early March. An animation of massive susnpot AR 2192 crossing the Earthward face of Sol from October 17th to October 29th, 2014. Credit: NASA/SDO. What’s is store for Cycle #25? One thing’s for certain: if the current trend continues, with spotless days more the rule than the exception, we could be in for a deep profound solar minimum through the 2018 to 2020 season, the likes of which would be unprecedented in modern astronomy. Fun fact: a similar dearth of sunspots was documented during the 1645-1715 period referred to as the Maunder Minimum. During this time, crops failed and the Thames River in London froze, making “frost fairs” along its frozen shores possible. Ironically, the Maunder Minimum also began just a few decades after the dawn of the age of telescopic astronomy. During this time, the idea of “spots on the Sun” was regulated to a controversial, and almost mythical status in mainstream astronomy. Full post
— gReader Pro